Rolling method and rolling apparatus for flat-rolled metal materials

ABSTRACT

The invention provides a rolling method for a flat-rolled metal material and a rolling apparatus for the method each capable of stably producing a flat-rolled metal material free from camber or having an extremely light camber. The method is a rolling method of a flat-rolled metal material executed by using a rolling mill including at least work rolls and backup rolls. The apparatus is a rolling mill for this method. A rolling direction force acting on roll chocks on the operator side and the driving, side of the work roll is measured, the difference of the rolling direction force between the operator side and the driving side is calculated and a left-right swivelling component of roll gap of the rolling mill is controlled on the basis of this difference.

TECHNICAL FIELD

This invention relates to a rolling method and to a rolling apparatusfor flat-rolled metal materials. More particularly, the inventionrelates to a rolling method and to a rolling apparatus, for flat-rolledmetal materials that can stably produce flat-rolled metal materials nothaving, or having extremely light, camber.

BACKGROUND ART

In a rolling process of a flat-rolled metal material, it is veryimportant to roll a sheet material in a form free from camber, or in aform not having bend in the left-right direction, in order to avoid notonly a plane shape defect and a dimensional accuracy defect of therolled material but also to avoid sheet pass troubles such as a zigzagmovement and a tail crash.

Incidentally, to simplify expressions, the operator side and the drivingside of the rolling mill, as the right and left sides when the rollingmill is seen from the front of the rolling direction, will be called“right and left”, respectively.

To cope with such problems, Japanese Unexamined Patent Publication(Kokai) No. 4-305304 discloses a camber control technology that arrangesdevices for measuring the lateral positions of the rolled material onthe entry and exit sides of the rolling mill, calculates the camber ofthe rolled material from the measured values and regulates the positionof an edger roll, arranged on the entry side of the rolling mill, tocorrect the camber.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No.7-214131 discloses a camber control technology that controls aleft-right difference of roll gap of the rolling mill, that is,reduction leveling, on the basis of a left-right difference in edgerroll loads provided on the entry and exit sides of the rolling mill.

Japanese Unexamined Patent Publication (Kokai) No. 2001-105013 disclosesa camber control technology that analyzes actual measurement values of aleft-right difference of rolling loads and controls a left-rightdifference of roll gap, that is, reduction leveling, or positions ofside guides.

Japanese Unexamined Patent Publication (Kokai) No. 8-323411 discloses amethod that conducts camber control by restricting a rolled material byan edger roll and a side guide on the entry side and a side guide on theexit side.

However, the invention relating to the camber control technology by thelateral position measurement of the rolled material described inJapanese Unexamined Patent Publication (Kokai) No. 4-305304 is basicallydirected to the correction of the camber that has already occurred andcannot substantially, in advance, prevent the occurrence of a camber.

According to the invention relating to the camber control technologybased on the edger roll load left-right difference on the entry and exitsides of the rolling mill and described in Japanese Unexamined PatentPublication (Kokai) No. 7-214131, it is difficult to acquire goodcontrol accuracy when the camber already exists in the rolled materialon the entry side because the camber operates as disturbance to theedger roll load difference on the entry side. The edger roll on the exitside must be saved back at the time of passing of the distal end of therolled material in order to avoid impingement, and it is difficult, too,to conduct camber control from the distal end of the rolled material.

According to the invention relating to the camber control technologybased on the rolling load left-right difference described in JapaneseUnexamined Patent Publication (Kokai) No. 2001-105013, the method ofestimating the camber from the left-right difference of the rolling loadhas extremely low accuracy and is not practical when the sheet thicknessof the rolled material on the entry side is not uniform in the sheetwidth direction or when the temperature distribution of the rolledmaterial is not uniform in the sheet width direction.

In the invention relating to the camber control by using the edger rollon the entry side, the side guide on the entry side and the side guideon the exit side and described in Japanese Unexamined Patent Publication(Kokai) No. 8-323411, the exit side camber can be made zero if the sideguide on the exit side can completely restrict the rolled material onthe exit side. However, because the side guide on the exit side must bekept greater than the sheet width of the rolled material in order tosmoothly carry out the rolling operation, the camber occurs on therolled material to an extent corresponding to this margin.

After all, it can be concluded that the problems of the prior arttechnologies described above result from the absence of the method thatcan measure and control very accurately and without a time delay thecamber that occurs owing to various causes.

It is therefore an object of the invention to provide a rolling methodfor a flat-rolled metal material and a rolling apparatus for the methodthat can advantageously solve the problems of the prior arttechnologies, regarding the camber control described above, and canstably produce a flat-rolled metal material not having, or havingextremely light, camber.

DISCLOSURE OF THE INVENTION

The gist of the invention for solving the problems of the prior arttechnologies is as follows.

(1) A rolling method for a flat-rolled metal material, for executingrolling by using a rolling mill having at least work rolls and backuprolls for a flat-rolled metal material, comprising the steps ofmeasuring a rolling direction force acting on roll chocks on a operatorside and a driving side of the work roll; calculating the difference ofthe rolling direction force between the operator side and the drivingside; and controlling a left-right swivelling component of roll gap ofthe rolling mill on the basis of the difference.

(2) A rolling method of a flat-rolled metal material as described in(1), further comprising the steps of measuring a camber of a rolledmaterial; and learning a control target value of the difference of therolling direction force between the operator side and the driving sideon the basis of the camber.

(3) A rolling apparatus for a flat-rolled metal material including arolling mill having at least work rolls and backup rolls, comprisingload detection devices for measuring a rolling direction force acting onwork roll chocks, arranged on both the entry side and the exit side ofthe roll chocks, in a rolling direction on both the work side and thedriving side of the work rolls.

(4) A rolling apparatus for a flat-rolled metal material as described in(3), further comprising a device for pressing the work roll chock in therolling direction, arranged on either one of the entry side and the exitside of the work roll chock in the rolling direction.

(5) A rolling apparatus for a flat-rolled metal material as described in(4), wherein the device for pressing the work roll chock in the rollingdirection is a hydraulic powered device.

(6) A rolling apparatus for a flat-rolled metal material as described in(4) or (5), further comprising a device for pressing the work roll chockin the rolling direction, arranged on the side opposite to the side inwhich the work roll is offset with the backup roll being the reference,of the entry side and the exit side of the work roll chock in therolling direction.

(7) A rolling apparatus for a flat-rolled metal material as described inany of (3) through (6), further comprising a calculation device forcalculating a difference of rolling direction force acting on the workroll chock between the operator side and the driving side on the basisof a measurement value by the load detection device; a calculationdevice for calculating a left-right swivelling component controlquantity of roll gap of the rolling mill on the basis of the calculationvalue of the difference of the rolling direction force between theoperator side and the driving side; and a control device for controllingthe roll gap of the rolling mill on the basis of the calculation valueof the left-right swivelling component control value of the roll gap.

(8) A rolling apparatus as described in any of (3) through (6), furthercomprising a camber measurement device for measuring camber of a rolledmaterial.

(9) A rolling apparatus for a flat-rolled metal material as described inany of (3) through (9), further comprising a calculation device forcalculating a difference of rolling direction force acting on the workroll chock between the operator side and the driving side on the basisof a measurement value by the load detection device; a calculationdevice for calculating a left-right swivelling component controlquantity of roll gap of the rolling mill on the basis of the calculationvalue; a control device for controlling the roll gap of the rolling millon the basis of the calculation value of the left-right swivellingcomponent control value of the roll gap; a camber calculation device formeasuring camber of the rolled material; and a calculation device forlearning a control target value of the difference of the rollingdirection force between the operator side and the driving side on thebasis of the camber measurement value by the camber measurement device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically showing a preferred form of a rollingapparatus relating to a rolling method of a flat-rolled metal materialaccording to: the invention described in (1) or a rolling apparatus, ofa flat-rolled metal material of the invention described in (7).

FIG. 2 is a view schematically showing another preferred form of therolling apparatus relating to the rolling method of a flat-rolled metalmaterial according to the invention described in (1) or the rollingapparatus of the flat-rolled metal material of the invention describedin (7).

FIG. 3 is a view schematically showing a preferred form of a rollingapparatus of a flat-rolled metal material according to the inventiondescribed in (3).

FIG. 4 is a view schematically showing another preferred form of therolling apparatus of the flat-rolled metal material according to theinvention described in (3).

FIG. 5 is a view schematically showing a preferred form of a rollingapparatus of a flat-rolled metal material according to the inventiondescribed in (4) or (5).

FIG. 6 is a view schematically showing a preferred form of a rollingapparatus of a flat-rolled metal material according to the inventiondescribed in (6).

FIG. 7 is a view schematically showing another preferred form of therolling apparatus of a flat-rolled metal material according to theinvention described in (6).

FIG. 8 is a view schematically showing a preferred form of a rollingapparatus relating to a rolling method of a flat-rolled metal materialaccording to the invention described in (2) or a rolling apparatus of aflat-rolled metal material of the invention described in (9).

FIG. 9 is a view schematically showing a preferred form of a rollingapparatus relating to a rolling method of a flat-rolled metal materialaccording to the invention described in (2) or a rolling apparatus of aflat-rolled metal material of the invention described in (9).

FIG. 10 is a graph showing a change in a relation, between a left-rightdifference of rolling direction force and a camber quantity, due to wearof the rolls and the like.

BEST MODE FOR CARRYING OUT THE INVENTION

A mode for carrying out the invention will be hereinafter explained.

Generally, the causes of the occurrence of camber in rolling offlat-rolled materials are a setting defect of a roll gap, a left-rightdifference of the thickness of the rolled material on the entry side anda left-right difference of deformation resistance of the rolledmaterial. Whichever the cause may be, the left-right difference occurseventually in longitudinal strain in a rolling direction due to rolling.Consequently, a forward slip and a backward slip change in a sheet widthdirection, and an exit-side speed and an entry-side speed of the rolledmaterial exhibit a left-right difference, to thereby cause the camber.At this time, during rolling, of a distal end portion of the rolledmaterial that is likely to invite the camber, for example, the length ofthe rolled material on the exit side for which rolling has already beenfinished is short and the exit-side speed causes the left-rightdifference under a relatively free state. In order for the entry-sidespeed to exhibit the left-right difference, the rolling material at theentry side must cause rigid rotation as a whole inside a horizontalplane. However, during rolling of the distal end portion, as a longnon-rolled material generally remains on the entry side, a momentagainst the rigid rotation described above occurs owing to the weight ofthe rolled material itself and to friction with a table roller. As thismoment is transmitted as a reaction to the work roll of the rollingmill, a left-right difference occurs in the rolling direction forceacting on the work roll chock portion and the moment is finallysupported.

According to the rolling method of the flat-rolled metal material of theinvention described in (1), the rolling direction forces acting on rollchocks on the operator side and the driving side of the work roll aremeasured and the difference between the rolling direction force on theoperator side and the rolling direction force on the driving side, thatis, the rolling direction force left-right difference, is calculated.Therefore, the moment acting mainly from the entry side rolled materialduring rolling of the distal end portion can be detected from thisvalue. This moment occurs only when the left-right difference of thelongitudinal strain that results in the occurrence of the camberdevelops as described above. Moreover, this moment occurs substantiallysimultaneously with the occurrence of the longitudinal straindifference. Therefore, the occurrence of the camber can be prevented inadvance by operating the left-right swivelling component of the roll gapof the rolling mill, that is, a reduction leveling, in such a directionthat reduces the rolling direction force left-right difference.

The principle described above holds true of rolling of the tail endportion of the rolled material at which the camber is most likely tooccur next to rolling of the distal end portion of the rolled material.During rolling of the tail end portion, the length of the rolledmaterial on the exit side, that has already been rolled, is large andthe moment occurs mainly from the exit side rolled material in such afashion as to withstand the longitudinal strain and the left-rightdifference of the forward slip when they are about to occur and istransmitted as the reaction to the work roll. In this case, too, theoccurrence of the left-right difference of the longitudinal stain can bedetected by measuring and calculating the left-right difference of therolling direction forces acting on the work roll chock. Consequently,the occurrence of the camber at the tail end portion can be prevented inadvance by operating the left-right swivelling component of the roll gapof the mill, that is, the reduction leveling, in a direction thatreduces the rolling direction force left-right difference.

As explained above, the method of the invention described in (1) detectsand measures the left-right difference of the longitudinal strain due torolling that may directly result in the occurrence of the camber, andimmediately executes the reduction leveling operation for making theleft-right difference uniform. Therefore, the method can provide rollingthat is substantially free from the occurrence of the camber or hasextremely light camber.

As described in (1), rolling substantially free from the occurrence ofthe camber becomes possible by the method that measures the rollingdirection force acting on the roll chocks on the operator side and thedriving side of the work roll, calculates the difference between therolling direction force on the operator side and the rolling directionforce on the driving side, that is, the rolling direction left-rightdifference and operates the reduction leveling of the rolling mill inthe direction that reduces this rolling direction force left-rightdifference.

In the method described above, however, when the left-right differenceof the roll diameter or the left-right difference of the frictionalcoefficient occurs due to the wears etc, of the rolls, there is thepossibility of the shift of the rolling direction force left-rightdifference. Therefore, even when reduction leveling is operated in thedirection that reduces the rolling direction force left-rightdifference, there remains the possibility that the occurrence of thecamber cannot be prevented sufficiently.

Therefore, to eliminate the possible problem described above, therolling method of the flat-rolled metal material of the inventiondescribed in (2) measures the rolling direction force acting on the rollchocks on the operator side and the driving side of the work roll,calculates the difference of the rolling direction force between theoperator side and the driving side, sets the control target value of therolling direction force left-right difference on the basis of thisdifference, that is, the rolling direction force left-right difference,when the reduction leveling control is executed, and executes thereduction leveling control so as to attain this control target value.This control target value is generally set to zero, and the inventionproposes a rolling method that measures the camber of the rolledmaterial after or during rolling and learns the control target value onthe basis of this camber actual measured value. When the control targetvalue is learnt in this way on the basis of the camber actual measuredvalue after rolling and sets the learnt control target value to rollingof this pass or the next pass, it becomes possible to correct deviationof the rolling direction force resulting from the wear, etc, of therolls, to correctly detect and measure the left-right difference of thelongitudinal strain with rolling that may directly result in theoccurrence of the camber, and to execute the reduction levelingoperation for making the left-right difference uniform. In this way,rolling substantially free from the occurrence of the camber or havingan extremely light camber can be accomplished.

Next, the invention relating to a rolling apparatus for executing therolling method of the flat-rolled metal material of the inventiondescribed in (1) will be explained.

In the rolling apparatus of the flat-rolled metal material of theinvention described in (3), the load detection devices are provided onboth entry side and the exit side of the rolling chocks in the rollingdirection on the operator side and the driving side of the work roll.Therefore, when the resultant force is calculated by taking directivityof the load measurement values on both entry and exit sides intoconsideration, the rolling direction force acting on the roll chocks onthe operator side and the driving side can be determined. Furthermore,the rolling method of the flat-rolled metal material described in (1)can be executed when the difference of the rolling direction forceacting on the roll chock on the operator side and the rolling directionforce acting on the roll chock on the driving side is calculated.

The rolling apparatus of the invention described in (4) has a device forpressing the work roll chock in the rolling direction on either theentry side or the exit side of the work roll chock in the rollingdirection. When rolling is carried out while the work roll chock ispressed in the rolling direction by such a device construction, themoment can be immediately detected as the rolling direction forceleft-right difference acting on the work roll chock when the moment actsfrom the rolled material on the work roll due to the left-rightdifference of the longitudinal stain as described above. Consequently, acamber control system having more excellent in response and accuracy canbe achieved.

In the rolling apparatus of the flat-rolled metal material of theinvention described in (5), the device for pressing the work roll chockin the rolling direction is a hydraulic powered device. Because thehydraulic powered device presses the work roll chock, the press forcecan be controlled to a low level that does not hinder the rollingoperation. Moreover, vibration of the work roll chock in the rollingdirection can be reduced and good control can be done to such an extentthat it can stabilize the chock position.

The rolling apparatus of the flat-rolled metal material of the inventiondescribed in (6) includes a device for pressing the work roll chock inthe rolling direction, arranged on the side opposite to the side inwhich the work roll is offset with the backup roll being the reference,of the entry side and the exit side of the work roll chock in therolling direction. According to this arrangement, the offset componentof force that occurs as a horizontal direction component of force of therolling load due to the work roll offset operates in the same directionas the press force created by the device described above. Consequently,the press force to be given so as to stabilize the rolling directionposition of the work roll chock becomes small and the size of thepressing device can be reduced. When the rolling direction press forceto the work roll chock becomes excessively great, the problem occurs inthe follow-up performance to the reduction position control duringrolling given by a sheet thickness control function but the occurrenceof such a problem can be avoided by reducing the press force by thisrolling direction press device.

The rolling apparatus for a flat-rolled metal material of the inventionfurther includes a calculation device for calculating a difference ofrolling direction force acting on the work roll chock between theoperator side and the driving side in addition to the rolling apparatusof the flat-rolled metal material described in any of (3) through (6).Therefore, the rolling apparatus can detect the moment resulting fromthe left-right difference of the longitudinal strain in the rollingdirection and acting from the rolled material onto the work roll thatmay result in the camber. Furthermore, the rolling apparatus includes acalculation device for calculating a left-right swivelling componentcontrol quantity of roll gap of the rolling mill on the basis of thecalculated value of the difference of the rolling direction forcebetween the operator side and the driving side, for making thelongitudinal strain uniform in the left-right direction and a controldevice for controlling the roll gap of the rolling mill on the basis ofthe calculated value of the left-right swivelling component controlvalue of the roll gap. Therefore, the rolling mill can prevent inadvance the occurrence of the left-right difference of the longitudinalstrain and can roll a flat-rolled metal material free from camber orhaving extremely light camber.

Next, the invention of the rolling apparatus for executing the rollingmethod of the flat-rolled metal material of the invention described in(2) will be explained.

The rolling apparatus of the flat-rolled metal material of the inventiondescribed in (8) includes load detection devices on both the exit sideand the entry side of the roll chocks in the rolling direction on theoperator side and the driving side of the work rolls in the same way asthe rolling apparatus of the invention described in (3). Therefore, whenthe resultant force is calculated by taking directivity of the loadmeasurement values on both entry and exit sides, the rolling directionforce acting on the roll chock on each of the operator and driving sidescan be determined even when the force acts in any of the entry and exitsides and the difference between the rolling direction force acting onthe operator side roll chock and the rolling direction force acting onthe driving side roll chock can be calculated. Furthermore, because therolling apparatus includes a camber measurement device, the controltarget value can be learnt on the basis of the camber actual record ofthe rolled material after the rolling and the rolling method of theflat-rolled metal material described in (2) can be executed.Incidentally, the rolling apparatus described in (8) can be equippedwith the device for pressing the roll chock in the rolling direction inthe same way as the rolling apparatuses described in (4) to (6).

The rolling apparatus of the flat-rolled metal material of the inventiondescribed in (9) includes a calculation device for calculating thedifference of the rolling direction force acting on the work roll chockbetween the operator side and the driving side in addition to therolling apparatus described in (8). Therefore, the rolling apparatus candetect the moment that results from the left-right difference of thelongitudinal strain in the rolling direction that may result in thecamber, and acts from the rolled material on the work roll. Because therolling apparatus further includes a calculation device for learning acontrol target value of the difference of the rolling direction forcebetween the operator side and the driving side on the basis of thecamber measurement value of the rolled material, the shift quantity canbe corrected by learning on the basis of the camber actual measurementvalue even when the difference of the rolling direction force acting onthe work roll chock shifts due to the wear, etc, of the rolls and thesuitable control target value can be calculated. Further, the rollingapparatus includes a calculation device for calculating a left-rightswivelling component control quantity of roll gap of the rolling millfor making the longitudinal strain uniform in the left-right directionon the basis of the calculation value, and a control device forcontrolling the, roll gap of the rolling mill on the basis of thecalculated value of the left-right swivelling component control value ofthe roll gap. Therefore, the rolling apparatus can prevent in advancethe occurrence of the left-right difference of the longitudinal strainand can roll a flat-rolled metal material free from the camber or havingan extremely light camber. Incidentally, the rolling apparatus describedin (9) may be provided with the press device for pressing the roll chockin the rolling direction in the same way as the rolling apparatusesdescribed in (4) to (6).

Next, the embodiment of the invention will be explained furtherconcretely with reference to the drawings.

FIG. 1 shows the rolling apparatus relating to the rolling methoddescribed in (1) or the rolling apparatus described in (7) according toa preferred embodiment of the invention.

A rolling mill includes an upper work roll 1 supported by an upper workroll chock 5, an upper backup roll 3 supported by an upper backup rollchock 5, for backing up the upper work roll 1, a lower work roll 2supported by a lower work roll chock 6 and a lower backup roll 4supported by a lower backup roll chock 7, for backing up the lower workroll 2. The rolling mill further includes a screw down device 13.Incidentally, a flat-rolled metal material 21 is rolled in a rollingdirection 22.

Though FIG. 1 basically shows only the apparatus construction on theoperator side, similar devices exist on the driving side, too.

The rolling direction force acting on the upper work roll 1 of therolling mill is basically supported by the upper work roll chock 5. Theupper work roll chock 5 is provided with an upper work roll chock exitside load detection device 9 and an upper work roll entry side loaddetection device 10. These load detection devices 9 and 10 can measurethe force acting between the members such as a project block (not shown)fixing the upper work roll chock 5 in the rolling direction and theupper work roll chock 5. To simplify the device construction, these loaddetection devices 9 and 10 preferably and ordinarily have a constructionfor measuring a compressive force. An upper work roll rolling directionforce calculation device 14 calculates a difference of measurementresults by the upper work roll exit side load detection device 9 and theupper work roll entry side load detection device 10 and also calculatesthe rolling direction force acting on the upper work roll chock 5. Asfor the rolling direction force acting on the lower work roll 2, a lowerwork roll rolling direction force calculation device 15 calculates therolling direction force acting on the work roll chock 6 on the basis ofthe measurement values of a lower work roll exit side load detector 11and a lower work roll entry side load detector 12 that are arranged onthe exit side and the entry side of the lower work roll chock 6.

Next, a work roll rolling direction resultant force calculation device16 calculates the sum of the calculation result of the upper work rollrolling direction force calculation device 14 and the calculation resultof the lower work roll rolling direction force calculation device 15 tocalculate the rolling direction resultant force acting on the upper andlower work rolls. This procedure is conducted not only for the operatorside but also for the driving side by using entirely the sameconstruction and the result is obtained as the work roll rollingdirection resultant force 17 on the driving side. A operatorside/driving side rolling direction force difference calculation device18 calculates the difference between the calculation results on theoperator side and on the driving side and in this way, the difference ofthe rolling direction force acting on the work roll chock between theoperator side and the driving side is calculated.

Next, a reduction leveling control quantity calculation device 19 setsthe difference of the rolling direction force acting on the work rollchock between the operator side and the driving side to a suitabletarget value and calculates a left-right swivelling component controlquantity on the basis of the calculation result of the difference of therolling direction force between the operator side and the driving sidefor preventing the camber. Here, the control quantity is calculated byPID calculation that takes a proportional (P) gain, an integration (I)gain and a differential (D) gain into consideration, for example. Areduction leveling control device 20 controls the left-right swivellingcomponent of the roll gap of the rolling mill on the basis of thiscontrol quantity calculation result and rolling free from the occurrenceof camber or having extremely slight camber can be accomplished.

In the device construction described above, only addition andsubtraction are basically done on the outputs of eight load detectiondevices on both operator side and driving side before the calculationresult of the operator side/driving sides rolling direction forcedifference calculation device 18 is obtained. Therefore, the deviceconstruction and the sequence of calculation described above may bearbitrarily changed. For example, it is possible to first add theoutputs of the upper and lower exit side load detection devices, then tocalculate the difference from the addition result on the entry side andto finally calculate the difference between the operator side and thedriving side. Alternatively, it is possible to first calculate thedifference of the outputs of the load detection devices at therespective positions on the operator side and the driving side, then tocalculate the sum of the upper and lower detection devices and tofinally calculate the difference between the entry side and the exitside.

FIG. 2 shows another preferred form of the rolling apparatus relating tothe rolling method of the invention described in (1) or the rollingapparatus of the invention described in (7). In the embodiment shown inFIG. 2, the detection device and the calculation device for the rollingdirection force acting on the lower work roll chock are omitted incomparison with the embodiment shown in FIG. 1. Generally, the momentresulting from the left-right difference of the longitudinal strain andacting from the rolled material on the work rolls does not always actuniformly on the upper and lower work rolls but the tendency of its timeseries change behavior does not reverse for the upper and lower workrolls. Therefore, when the suitable control gain is set in the reductionleveling control quantity calculation device 19, excellent cambercontrol can be accomplished on the basis of the left-right difference ofthe rolling direction force acting on either one of the upper and lowerwork rolls.

In the embodiments shown in FIGS. 1 and 2, the left-right swivellingcomponent of the roll gap is the direct control parameter but in thecase of extremely light reduction rolling such as skin pass rolling, therolling operation is executed in many cases with the rolling load as thetarget value. In such a case, the left-right difference of the rollingload may be calculated as the control target value. In other words; thecontrol quantity of the left-right difference of the rolling load iscalculated in such a direction that eliminates the left-right differenceof the rolling direction force acting on the work roll chock on thebasis of this left-right difference of the rolling direction force andwhen the loading load control is made with this control quantity as thetarget value, the left-right swivelling component of the roll gap can beeventually controlled.

FIG. 3 shows a preferred form of the rolling apparatus of the inventiondescribed in (3). In the rolling apparatus shown in FIG. 3, a rollbalance device (not shown in the drawing) built in project blocks 24 and25 fixed to a housing 23 support the work roll chock in a verticaldirection. Incidentally, the rolling apparatus includes a rolling loaddetection device 26 between the reduction device 13 and the upper backuproll. To measure the rolling direction force acting on the upper workroll chock 5, the upper work roll exit side load detection device 9 isinterposed between the exit side project block 24 and the upper workroll chock 5 and the upper work roll entry side load detection device 10is interposed between the entry side project block 24 and the upper workroll chock 5. To measure the rolling direction force acting on the lowerwork roll chock the lower work roll exit side load detection device 11is interposed between the exit side project block 24 and the lower workroll chock 6 and the lower work roll entry side load detection device 12is interposed between the entry side project block 25 and the lower workroll chock 6. Because the load detection devices are arranged in thisway on both entry and exit sides, the magnitude of the force can becorrectly measured even when the rolling direction force acts in anydirection on the work roll chocks.

FIG. 4 shows another preferred form of the rolling apparatus of theinvention described in (3). In the rolling apparatus shown in FIG. 4,the upper backup roll chock 7 is of the type that embraces the upperwork roll chock 5. In this case, to measure the rolling direction forceacting on the upper work roll chock 5, the upper work roll exit sideload detection device 9 and the upper work roll entry side loaddetection device 10 are interposed between the upper work roll chock 5and the upper backup roll chock 7. In this case, too, the magnitude ofthe force can be correctly measured even. when the rolling directionforce acts in any direction on the work roll chocks because the loaddetection devices are arranged on both entry and exit sides of the workroll chock.

FIG. 5 shows a preferred form of the rolling apparatus of the metalsheet material of the invention described in (4) or (5). In the rollingapparatus of the flat-rolled metal material shown in FIG. 5, an entryside work roll chock press device 27 is arranged adjacent to the upperwork roll entry side load detection device 10 on the entry side of theupper work roll chock 5 and this press device 27 presses the work rollchock 5 from the entry side to the exit side with predetermined pressforce. This construction can stabilize the rolling direction position ofthe upper work roll chock 5 and can improve response and accuracy of themeasurement of the rolling direction force acting on the upper work rollchock 5. Incidentally, in the rolling apparatus shown in FIG. 5, theentry side work roll chock press device 27 is a hydraulic powereddevice. When such a construction is employed, even when the work rollchock momentarily vibrates in the rolling direction such as when therolled material is caught, a stable press force operates and themovement of the work roll chock can be stabilized.

FIG. 6 shows a preferred form of the rolling apparatus of theflat-rolled metal material of the invention described in (6). In therolling apparatus of the flat-rolled metal material shown in FIG. 6, theupper work roll is offset by Δx on the entry side and the entry sidework roll chock press device 27 is arranged on the entry side of theupper work roll chock 5. According to this construction, the offsetforce acting from the upper backup roll 3 on the upper work roll 1operates in such a direction as to press the upper work roll chock 5 inthe exit side direction and the force of the entry side work roll chockpress device 27 can be decreased, so that the setup can be renderedcompact in scale and economical. At the same time, because the clampingforce of the upper work roll chock 5 can be decreased, disturbancefactors, for other controls, can be reduced, too. Incidentally, theupper work roll entry side load detection device 10 is omitted in therolling apparatus of the flat-rolled metal material shown in FIG. 6 butthis is the example where the hydraulic powered device itself is used asa substitute for the load detection device by arranging a sensor (notshown) for measuring an operation oil supplied to the hydraulic cylinderof the entry side work roll chock press device 27 as the hydraulicpowered device in FIG. 6.

FIG. 7 shows another preferred form of the rolling apparatus of theflat-rolled metal material of is the invention described in (6). In therolling apparatus of the flat-rolled metal material shown in FIG. 7, anexit side work roll chock position control device 28 is arranged on theexit side of the upper work roll chock in addition to the form shown inFIG. 6. This exit side work roll chock position control device 28 isalso a hydraulic powered device. In the rolling apparatus shown in FIG.6, the upper work roll chock 5 is structurally interposed between theentry and exit side hydraulic cylinders but in the case of the exit sidework roll chock position control device 28, an exit side work roll chockposition detection device 29 is disposed to execute position control,and the clamping force of the chock is given by the entry side work rollchock press device. According to such a construction, an additionalcontrol capacity such as adjustment of the offset quantity of the workroll or a minute cross angle between the backup rolls can be acquired.

Incidentally, the embodiments shown in FIGS. 5, 6 and 7 represent theexamples where the work roll chock press device is arranged on the entryside of the rolling mill but it may also be arranged on the exit side.However, the relative positional relation with the work roll offset mustbe maintained.

The embodiments shown in FIGS. 5, 6 and 7 represent the embodiments onlyin the proximity of the upper work roll chock, but the embodiment whenapplied to the lower work roll chock is basically the same.

Next, FIG. 8 shows another preferred form of the rolling apparatus ofthe flat-rolled metal material relating to the rolling method of theinvention described in (2) or the rolling apparatus described in (9).Incidentally, FIG. 8 basically shows only the apparatus construction onthe operator side but a similar apparatus exits on the driving side,too. The rolling direction force acting on the upper work roll 1 isbasically supported by the upper work roll chock 5. The upper work rollchock is provided with the upper work roll chock exit side loaddetection device 9 and the upper work roll entry side load detectiondevice 10 and can measure the force acting between members such as aproject block (not shown) and the upper work roll chock. To simplify theapparatus construction, these load detection devices preferably andgenerally have a construction for measuring the compressive force. Theupper work roll rolling direction force calculation device 14 calculatesthe difference of the measurement results between the upper work rollexit side load detection device 9 and the upper work roll entry sideload detection device 10 and also calculates the rolling direction forceacting on the upper work roll chock 5. As for the rolling directionforce acting on the lower work roll 2, too, the lower work roll rollingdirection force calculation device 15 calculates the rolling directionforce acting on the lower work roll chock 6 on the basis of themeasurement results of the lower work roll exit side load detectiondevice 11 and the lower work roll entry side load detection device 12that are provided on the exit side and entry side of the lower work rollchock 6, respectively. Next, the lower work roll rolling directionresultant force calculation device 16 calculates the sum of thecalculation result of the upper work roll rolling direction forcecalculation device 14 and the calculation result of the lower work rollrolling direction force calculation device 15 to calculate the rollingdirection resultant force acting on the upper and lower work rolls. Theprocedure described above is executed not only on the operator side butalso on the driving side by using entirely the same apparatusconstruction and the result is obtained as the work roll rollingdirection resultant force 17 on the driving side. The operatorside/driving side rolling direction force difference calculation device18 calculates the difference between the calculation result on theoperator side and the calculation result on the driving side, so thatthe difference of the rolling direction force acting on the work rollchock on the operator side and the driving side, that is, the rollingdirection force left-right difference, is calculated.

Next, the control target value calculation device 31 calculates thecontrol target value of the rolling direction force left-rightdifference and this calculation method will be explained. Generally, thecontrol target value of the rolling direction left-right difference iszero and the occurrence of the camber can be prevented by controllingthe left-right swivelling component of the roll gap of the rolling millso that the rolling direction force left-right difference reaches thiscontrol target value. However, when the left-right difference of theroll diameter occurs due to wear of the roll, etc, or when theleft-right difference of the frictional coefficient occurs, the rollingdirection force left-right difference is likely to shift due to thesefactors and in this case, the control target value is not set to zerobut must be changed to a suitable value. FIG. 1 is a graph showing thechange of the relation between the rolling direction force left-rightdifference due to wear, etc, of the roll and the camber quantity. Asshown in FIG. 10, the relation line A, between the rolling directionforce left-right difference and the camber quantity, shiftssubstantially parallel as indicated by the relation line B due to thewear, etc, of the roll. In this case, to make the camber quantity zero,a control target value A′ must be changed to a control target value B′.The shift of the relation line between the rolling direction forceleft-right difference and the camber quantity and the change of thecontrol target value can be easily judged by measuring the camberquantity during, or after, rolling. In other words, it will be assumedthat when control is executed to acquire the control target value A′ asshown in FIG. 10, the camber actual measurement value is not zero butthe camber actual measurement value is C. Then, it is possible to judgethat the relation between the rolling direction force left-rightdifference and the camber quantity shifts as represented by the line B.Therefore, the control target value may well be changed to a targetvalue Be in this pass or in the next pass or in rolling of the nextmaterial. Because this deviation of the rolling direction forceleft-right difference resulting from the wear of the roll possiblychanges with the increase of the number of passes of rolling, thecontrol target value must always be learnt and changed, too.Incidentally, symbols α_(A) and α_(b) in the graph represent thegradients of the relation lines A and B between the rolling directionforce left-right difference and the camber quantity, respectively. Theyare constants that are determined by the size of the rolling mill, therolling condition, deformation resistance of the rolled material, and soforth. When these gradients change due to the wear of the roll, etc, thegradients must be determined in advance by conducting preparatoryexperiments. However, α_(A) and α_(B) may be regarded as substantiallyequal and may be set to α_(A)=α_(B) (=α) by primary approximation whenthe conditions are satisfied, though these values change depending onthe rolling condition and the rolling material. However, as these valuesmay change with time, the value α_(B) may be periodically measured.

Therefore, the invention conducts learning of the control target valueof the rolling direction force left-right difference by the followingmethod. As shown in FIG. 8, a camber measurement device 30 is providedto the back of the rolling mill and can measure the camber of the rolledmaterial during or after rolling. The value of the camber quantity someasured is sent to the control target value calculation device 31. Thecontrol target value calculation device 31 calculates the control targetvalue in this pass or the next pass or during rolling of the nextmaterial by the method described above on the basis of this measurementvalue of the camber quantity. This control target value must be learntand changed with the increase of the number of passes of rolling andmust be learnt for each pass or for a predetermined number of rollingpasses in accordance with the following formula <1>:C ^((n)) =C _(r) ^((n−1)) ×γ+C ^((n−1))×(1−y)   <1>

Here, C^((n)) represents the control target value of the nth pass or nthrolled material, C_(r) ^((n)) is the control target value corrected onthe basis of the camber actual value of the nth pass or the nth rolledmaterial and γ is the learning gain (0 to 1.0).

The rolling reduction leveling control quantity calculation device 19calculates the left-right swivelling component control quantity of theroll gap of the rolling mill for preventing the camber on the basis ofthe calculation result of the difference between the control targetvalue and the rolling direction force on the operator side and thedriving side. Incidentally, in the stage in which the camber quantity ofthe first rolling is not actually measured, the control target value maybe the value of the rolling direction force left-right differenceoccurring at the time of fastening of a kiss roll or zero, for example.Here, the left-right swivelling component control quantity of the rollgap is calculated by PID calculation taking the proportional (P) gain,the integration (I) gain and the differential (D) gain intoconsideration, for example, for the control target value determined fromthe left-right difference of the rolling direction force and from theformula (1). The reduction leveling control device 20 controls theleft-right swivelling component of the roll gap of the rolling mill onthe basis of this control quantity calculation result and rolling freefrom the occurrence of the camber or having extremely light camber canbe accomplished. Incidentally, to change the control target value inthis pass, the control target value may be changed during rolling at thestage in which the camber quantity is actually measured.

FIG. 9 shows another preferred form of the rolling apparatus relating tothe rolling method of the invention described in (2) or the rollingapparatus of the invention described in (9). In the embodiment shown inFIG. 9, the detection devices and the calculation devices of the rollingdirection force acting on the lower work roll chock are omitted incomparison with the embodiment shown in FIG. 8. Generally, the momentresulting from the left-right difference of the longitudinal strain andacting from the rolled material on the work rolls does not always actuniformly on the upper and lower work rolls. Though the tendency of itstime series change behavior does not reverse for the upper and lowerwork rolls, the zero point of the rolling direction force left-rightdifference may shift. In this case, too, the camber of the rolledmaterial is measured during or after rolling and the control targetvalue learnt from this camber actual measurement value is set to thispass or to the next pass or rolling of the next material. As thedeviation of the rolling direction force left-right difference can becorrected in this way, excellent camber control can be accomplished onthe basis of the left-right difference of the rolling direction forceacting on either one of the upper and lower work rolls.

Incidentally, in the embodiments shown in FIGS. 8 and 9, too, the workroll chock press device may be arranged on the entry side of the rollingmill in the same way as in the embodiments shown in FIGS. 5, 6 and 7 ormay be arranged on the exit side, on the contrary. However, the relativepositional relation with the work roll offset shown in FIGS. 6 and 7must be maintained.

The embodiments shown in FIGS. 5, 6 and 7 may be likewise applied to thelower work roll chock, too.

EXAMPLE

An example where the sheet rolling method of the invention described in(2) is executed by using the rolling mill shown in FIG. 8 will beexplained. Learning of the control target value of the rolling directionforce left-right difference that is based on the output of the cambermeasurement device 30 provided to the back of the rolling mill isexecuted while the learning gain is set to γ 0.3 and the control targetvalue in the initial stage is set to zero. Incidentally, a constantwithin the range of 0.5 to 20 tonf/(mm/m) is set for each rollingcondition and each rolling material as a constant α representing thegradient of the relation line between the rolling direction forceleft-right difference and the camber quantity.

Table 1 tabulates the control target values of the rolling directionleft-right difference with respect to the typical number of rollingpasses and the actual measurement value of the camber. As can beunderstood from Table 1, the camber actual measurement value per meteris limited to a small value of 0.15 mm/m or below in each of the typicalnumbers of rolling passes. It can be understood, too, that the controltarget value of the rolling direction force left-right differencechanges depending on learning based on the camber actual measurementvalues as the number of rolling passes increases. The change of thecontrol target value presumably results from the wear of the backuprolls and the work rolls, etc. Because those methods which do notconduct learning of the control target value as is done in the sheetrolling method of the invention execute control inclusive of these errorfactors, the camber may presumably become greater in comparison with themethod of the invention.

TABLE 1 final rolling final rolling final rolling pass of first pass of300^(th) pass of 500^(th) rolled rolled rolled material materialmaterial control target value of 0 22 44 rolling direction left-rightdifference (tonf, operator side- driving side) camber actual 0.15 0.10.14 measurement value (mm/m)

As described above, the sheet rolling method of the invention learns thecontrol target value on the basis of the camber actual measurement valueafter rolling, sets this learnt control target value to rolling of thenext pass, corrects deviation of the rolling direction force left-rightdifference and can correctly detect and measure the left-rightdifference of the longitudinal strain due to rolling that is the directcause of the occurrence of the camber. It has been confirmed that whenthe rolling reduction leveling operation for rendering the left-rightdifference uniform is executed, rolling with extremely light camber canbe steadily made irrespective of the number of rolling passes.

INDUSTRIAL APPLICABILITY

It becomes possible to steadily and stably produce flat-rolled metalmaterials free from camber or having an extremely light camber withoutdepending on the number of rolling passes when the rolling method of theflat-rolled metal material and the rolling apparatus according to theinvention are used, and drastic improvements can be achieved in therolling process of the flat-rolled metal material and in the productionyield.

1. A rolling method of a flat-rolled metal material, for executingrolling by using a rolling mill having at least flat-rolled metalmaterial horizontal work rolls and backup rolls, comprising the stepsof: measuring rolling direction force acting on roll chocks on anoperator side and a driving side of said work rolls; calculating thedifference of said rolling direction force between the operator side andthe driving side; and controlling a left-right difference of roll gap ofsaid rolling mill on the basis of said calculated difference.
 2. Arolling method of a flat-rolled metal material according claim 1,further comprising the steps of: measuring camber of a rolled material;and learning a control target value of the difference of said rollingdirection force between the operator side and the driving side on thebasis of said camber.
 3. A rolling apparatus for a flat-rolled metalmaterial including a rolling mill having at least flat-rolled metalmaterial horizontal work rolls and backup rolls, comprising: loaddetection devices for measuring rolling direction force acting on workroll chocks, arranged on both entry side and exit side of said rollchocks in a rolling direction on both operator side and driving side ofsaid work rolls, and a calculation device for calculating rollingdirection force acting on said work roll chocks on a basis of adifference of the measured value between the entry side and the exitside of said load detection devices.
 4. A rolling apparatus for aflat-rolled metal material according to claim 3, further comprising: adevice for pressing said work roll chock in the rolling direction,arranged on either one of the entry side and the exit side of said workroll chock in the rolling direction.
 5. A rolling apparatus for aflat-rolled metal material according to claim 4, wherein said device forpressing said work roll chock in the rolling direction is a hydraulicpowered device.
 6. A rolling apparatus for a flat-rolled metal materialaccording to claim 4 or 5, further comprising: a device for pressingsaid work roll chock in the rolling direction, wherein said work roll isoffset with respect to said backup roll, said device for pressingarranged on the side opposite to the side in which said work roll isoffset, of the entry side and the exit side of said work roll chock inthe rolling direction.
 7. A rolling apparatus for a flat-rolled metalmaterial according to claim 3, 4 or 5 further comprising: a calculationdevice for calculating a difference of rolling direction force acting onsaid work roll chock between the operator side and the driving side onthe basis of a measurement value by said load detection device; acalculation device for calculating a left-right difference controlquantity of roll gap of said rolling mill on the basis of thecalculation value of the difference of said rolling direction forcebetween the operator side and the driving side; and a control device forcontrolling the roll gap of said rolling mill on the basis of thecalculation value of the left-right difference control value of the rollgap.
 8. A rolling apparatus for a flat-rolled metal material accordingto claim 3, 4 or 5 further comprising: a camber measurement device formeasuring camber of a rolled material.
 9. A rolling apparatus for aflat-rolled metal material according to claim 3, 4 or 5 furthercomprising: a calculation device for calculating a difference of rollingdirection force acting on said work roll chock between the operator sideand the driving side on the basis of a measurement value by said loaddetection device; a calculation device for calculating a left-rightdifference control quantity of roll gap of said rolling mill on thebasis of the calculation value; a control device for controlling theroll gap of said rolling mill on the basis of the calculation value ofthe left-right difference control value of the roll gap; a cambermeasurement device for measuring camber of the rolled material; and acalculation device for learning a control target value of the differenceof said rolling direction force between the operator side and thedriving side on the basis of the camber measurement value by said cambermeasurement device.